1. What are Globals in OOAD, if one exist? Does this have to do with visibility?
2. In a use case diagram, 3 use cases are connected to the 4th one by a dashed arrow. How to know the relationship <<include>> or <<extend>>? There is no text, just diagram.
3. By looking at the class diagram, how to find out whether it's specification or implementation perspective? Conceptual perspective is not a problem, because there won't be any operations, just attributes in it.

1. You can achieve globals in OOAD using static or class level attributes. The visibility would be public.

3. Another distinction is that class diagrams for domain models use labels for associations that reflect the nature of the association (see the POS domain model in Larman's Applying UML and Patterns, 3rd edition, page 157), whereas class diagrams at the design level label associations in a way that looks more like in an instance level attribute.